1. Technical Field
The present invention relates to an image reading apparatus and an image forming apparatus.
2. Related Art
An image reading apparatus provided with LEDs installed to a substrate, and a light guide that guides light emitted from the LEDs has been proposed. Specifically, configuration is made with the light emitted from the LEDs (point light sources) introduced into the light guide from an incident face of the light guide, and is reflected within the light guide and guided to an emitting face of the light guide.
The image reading apparatus raises the light intensity in a short-axis direction (slow scanning direction) at the face of an original by light emitted from the LED's being reflected in the light guide under conditions of substantially total internal reflection, and guided to the emitting face of the light guide. Further, the shape of the incident face of the light guide is optimized so that a light guide shape is obtained in which the illumination light is illuminated at a uniform intensity onto the original face by controlling the angle of light-rays in a long-axis direction (fast scanning direction). Furthermore, a reflecting portion is provided at the opposite side to the emitting side of the light guide, in order to raise the light illumination efficiency onto the image reading target region.
In the image reading apparatus, in order to ensure precision of reading, it is necessary to suppress fluctuations in the position and fluctuations in light intensity of the light source that irradiates light onto the image. However, when plural light sources, such as LED's or the like, are disposed in a row on one face of a substrate, if the substrate deforms due to heat given by the light sources, the position of the light sources may change and the light source intensity may also change.